1. Introduction

Abstract

Clay, noun. Old English Claég . A stiff viscous earth. (Blackies Compact Etymological Dictionary. Blackie & Son, London and Glasgow. 1946. War Economy Standard) Clay: The original Indo-European word was ‘gloi-’, ‘gli-’ from which came ‘glue’ and ‘gluten’. In Germanic this became ‘klai’, and the Old English ‘claeg’ became Modern English ‘clay’. From the same source came ‘clammy’ and the northern England dialect ‘claggy’ all of which describe a similar sticky consistency. (Oxford English Dictionary and Ayto's Dictionary of Word Origins, Bloomsbury, 1999) Clay: from Old Greek γλi;α, γλοi;α “glue”, γλi;υή “slime, mucus”, γλοi;ός “anything sticky” from I.-E. base *glei-, *gli- ‘to glue, paste stick together (Klein E. A comprehensive etymological dictionary of the English language. Elsevier, Amsterdam, 1967; Skeat W. An etymological dictionary of the English language. Oxford University Press, 1961; Mann S.E. An Indo-European comparative dictionary, Buske Verlag, Hamburg, 1987) 1.1. Clay Definitions of clay are given in Section 1.2. The uses of clay are ubiquitous and diverse. On a world scale, clay is of major economic significance, touching virtually every aspect of our everyday lives, from medicines to cosmetics and from paper to cups and saucers. It is very difficult to over-estimate its use and importance. The treatment of clay in this book is therefore wide ranging to reflect this situation. The occurrence of clay is also ubiquitous and diverse (see Text Box below) and, with its various mineral species, properties and behavioural characteristics, the industrial applications of clay are thus manifold and complex. As well as their traditional